With the development of science and technology, the audio outputting device (such as earphone, speaker, and so on) has been extensively applied in various fields. The audio outputting device has been roughly divided into two categories: one category is an analog connection audio outputting device (that is, the audio outputting device supports the inputting of the analog signal) which has the traditional 3.5 mm interface (that is, the coaxial audio plug has a diameter of 3.5 mm), the other category is an digital connection audio outputting device (that is, the audio outputting device supports the digital signal inputting) having the recently rising digital interface (such as the USB interface and so on).
However, as the digital connection audio outputting device is newly developing, the application field of the digital connection audio outputting device is relatively small, most of the audio device users use the analog connection audio outputting device, especially, in the headset users, the enormous application camp of 3.5 mm interface is formed, when user needs to listen to the audio in the sound source device which only supports the digital interface, as user often can only achieve the audio outputting device which supports the 3.5 mm interface, and have to transmit the digital signal audio in the sound source device to a storing device having the 3.5 mm interface and the digital interface by data line, then connect the analog connection audio outputting device with the storing device to listen to corresponding audio, which causes a technical problem that the operation of listen to the audio in the digital connection device is tedious, and time-consuming. So that digital analog converter (the converter can converse the digital signal outputted from the 3.4 mm interface to the analog signal supporting the digital interface) generates as the requirement, however, the volume of the digital analog converter is small, user is prone to loses or forgets to carry the digital analog converter, which causes that user cannot listen to the analog signal sound source by the digital connection audio outputting device in time.